1. Field of the Invention
The present invention generally relates to a thin film magnetic memory device. More particularly, the present invention relates to a randomly accessible thin film magnetic memory device with a memory cell having a magnetic tunnel junction (MTJ).
2. Description of the Background Art
An MRAM (Magnetic Random Access Memory) device has been attracting attention as a memory device capable of non-volatile data storage at low power consumption. The MRAM device is a memory device that stores data in a non-volatile manner using a plurality of thin film magnetic elements formed on a semiconductor integrated circuit and is capable of random access to each thin film magnetic element.
In particular, it has recently been reported that a dramatic improvement in performance of an MRAM device can be achieved through the use of a tunnel magnetic resistance element utilizing a magnetic tunnel junction as a memory cell. An MRAM device with a memory cell having a magnetic tunnel junction is disclosed, for example, in “A 10 ns Read and Write Non-Volatile Memory Array Using a Magnetic Tunnel Junction and FET Switch in Each Cell,” ISSCC Digest of Technical Papers, TA7.2, February 2000.
In such an MRAM device, in order to write a data signal to a tunnel magnetic resistance element, a prescribed write current needs to be passed through each of a digit line and a bit line. In the conventional MRAM device, however, a problem has arisen that the write current varied due to a variation in a power supply voltage or the like and thus stable writing of data could not be achieved.